Dual two-stage cracking apparatus for petroleum oils



E. A. OCON Aug. 10, 1937.

DUAL TWO-STAGE CRACKING APPARATUS FOR PETROLEUM OILS Filed April 10,1956 39 wiwmfi w IIIIII W R.

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Patented Aug. 10, 1937 DUAL 'TWO-STAGE CRACKING APPARATUS FOR PETROLEUMOILS Ernest A. Occn, New York, N. Y.

Application April 10, 1936, Serial No. 73,616

Claims.

This application is a continuation in part of my application filedDecember 2'7, 1933, Serial No. 704,174,.nowU. S..Patent 2,052,148 as tothe apparatus disclosed in saidapplication, certain 5 improvementshaving been added thereto.

In the present apparatus, a furnace is divided into two sections by anintermediate wall so as to provide two separate heat-receiving areas.Each section is divided into a combustion area -and a convection area.

Within each convection areais disposed an initial charging stockvaporizing coil and a secondstage cracking coil adapted forintercommunication, and in the combustion section is disposed one or aplurality of first-stage cracking coils, certain of the tubes thereofbeing catalytic tubes. Within each heating area is also disposed a steamsuperheater adapted for, discharge into the initial first-stage cracking.coil and also into the vaporizing coil.

Aycharacteristic of the apparatus is that a wallseparating the twoheating areas contains tubes through which liquid, such as burner. fuelis passed, absorbing heatby conduction from 5 said wall and notonlyincreasing the life of the latterbut serving asan element in the controlof the temperature of either or both convection sections underoperation.v

Bymeans of a communication between the second-stage cracking coil andthe vaporizing coil of either section, control ofv the temperature ofthe vapors in;their-.second-stage cracking may be effected vbydischarging, into the second-stage cracking-coil a suitable. proportionof the relatiVB1y COQ1 oilsteam vaporsfrom the vaporizing coil. r

The apparatus enables the operation of the two 'independent units underdifierent thermal and/or pressure conditions and a simultaneous 40,dischargingof thecracked products for blend- -ingandsimultaneoustreatment. For example, one section of-thefurnace may. beoperated to produce-highlysaturated light products and the, secondsection operated for theproduction of light products-of less saturation,and the cracked vapors from thetwo sections may be blended andfractionated to. .produce high anti-knock motor fuel.

The invention will-be. described with reference to. the accompanyingdrawing in which:--

Figure 1 is a diagrammatic view of an apparatusconstructed in accordancewiththe invention.

Figure 2 is adetailed.viewin sectionshowing a Venturi connection,between, the. vaporizing 0011 and the second-stagecracking, coil,whereby a the coils may be operated under relatively differentpressures, and at the same time, a pre determined proportion of thevapors from the vaporizing coil will be mixed with the vapors enteringsecond-stage cracking.

Referring to the drawing, A designates a dual furnace (of fire brick orother refractory material capable of withstanding the required internaltemperature), divided into two independent areas by wall B, each areahaving a combustion section C or Cat and a convection section D or Dr.

The charging stock passes into convection section D through pipe i,preferably after first receiving heat froma suitable source, as, forexample, a heat exchanger (not shown). The preheated charging stockenters the vaporizing coil 2 and the charging stock vapors thus produced pass into pipe 3. The lower end of pipe 3 is connected with thefirst-stage cracking coils 4, 4m, in the combustion section C, whichcoils receive superheated steam through pipe 5, from superheater coil 6located within the combustion section C at the top of the furnace. Thesteam superheater coil also discharges through a branch pipe "Icommunicating with the charging stockof pipe i so that additional heatis imparted to the charging stock and the viscosity of l the latter islowered prior to the vaporizing action of coil 2.

After leaving the first-stage cracking coils 4, 4.1:, in the combustionzone, the vapors under cracking reactions pass to pipe 8 which transfersthe vapors to the second-stage cracking coil 9.

Control of the temperature of the vapors entering the second-stagecracking is effected by manipulating a valve iii in pipe 3 which valvecontrols the passage of the uncracked vapors through a venturi i 1,Figure 2, the nozzle of which projects into the pipe 9a: which effectscommunication between coil 2 and the second-stage cracking coil 9.

In the second heating area of the furnace, the charging stock preferablymixed with superheated steam from pipe l2, enters vaporizing coil 250from pipe ix. The vapors thus produced are led to pipe 31: communicatingwith the first-stage cracking coils M, Mr, in the combustion section Cw,the first-stage cracking coils discharging into a pipe. l5 connectedwith the second-stage cracking coil i6.

Pipe 30: is also in communication with a Venturi tube of the sameconstruction as that shown in Figure 2 at i I, having its nozzledischarging into the second-stage cracking coil l6 so that bymanipulating valve like a predetermined proportion of therelatively coolvapors may be injected into the second-stage cracking coil forregulating the temperature of the vapors undergoing final crackingreactions.

In each combustion section I have shown a burner I! receiving fuel frompipe l8 communicating with pipe I83: receiving fuel from heat absorbingcoils l9 disposed in the upper part of wall B which divides the furnaceinto two heating sections. Coil 23 is adapted to receive any fluid usedin the process such as hydrogenous vapors or gas, as, for example,cracked hydrocarbon gas, preferably cool. It has a double function ofcooling wall B, and secondly, absorbing heat from the upper portion ofeither or both convection sections D, Dr, in accordance with thequantity of cool fluid passed therethrough, to secure, as one function,jointly with the action of the Venturi tubes l l and valves H] asatisfactory control of the thermal reactions. The Venturi tubes enablethe use of a higher pressure in either one of the coils 2 and 9, oreither one of the coils 2m and IS, without disturbance in the normalaction of the connected coil.

I prefer that the tubes of the second-stage cracking coil 9 or it belarger in diameter than the tubes of the first cracking stage 3, 4x orI4, Mx, so that there will be a drop of pressure in the vapors when theyare passed to the secondstage cracking coil in either case.

Instead of leading burner fuel through coils 23 in the division wall I3,I may lead any fluid for subsequent passage to the coils or one of them.For example, by closing the valves 25 and opening the valves 22, asupplementary or primary flow of charging stock or any flow-materialdesirable for addition to the primary charging stock,

, may be passed through pipes Him connected with pipes l I at, andthence to the inlet of coil 2 or the inlet of coil 23:, or to both coilssimultaneously.

A distinct advantage of the apparatus is that if the coils of one of theheating sections need cleaning or the activity of the catalytic tubes ifused has been substantially lowered, by shutting off the feed of thehydrocarbon material from the affected circuit and allowing steam toflow therethrough until the affected coils are cleaned and the cloggingmaterial removed, and/or activity of the catalysts recovered, then byturning on the heat and supply of hydrocarbon material,

the complete'unit starts operation at once and without stopping the flowthrough the second unaffected heating section. Also, by shutting off theheat and feed of the hydrocarbon material from an afiected circuit ofthe unit, the coils may be cleaned, repaired or replaced withoutaifecting the operation of the second heating section.

The catalytic tube may be made of, or lined with, a suitable catalyticmaterial, say, chromenickel-steel.

In the operation of the apparatus, the charging stock from any suitablesource passing through either one or both of pipes l, meets a blast ofsuperheated steam. The steam-oil vapors pass through the appropriatevaporizing coil and the oil-steam vapors may reach a temperature ofincipient cracking in its vaporizing coil. The oilsteam vapors thencepass through the two sections of the first-stage cracking coils in theappropriate combustion area, and thence pass into the appropriatesecond-stage cracking coil, which, by reason of the Venturi tube l I maybe operated under any desired pressure relatively to the vaporizingcoils.

By opening valve H0 or low a desired degree, a

' suitable proportion of the uncracked but vaporized oil-steam mixturewill be passed directly from the appropriate vaporizing coils into thesecond-stage cracking coils to control the temperature of the vaporstherein and to effect a rapid cracking action upon the uncracked vapors.It has been pointed out above that the second-stage cracking coils arepreferably of larger diameter than the coils of the first stage. I alsoprefer that the second-stage cracking coils be greater in length thanthe coils of the first stage.

I have placed in the outflow pipes for the cracked products, l9 and I92;pressure control valves 20, 20:0, the operation of which is wellunderstood in the art. By means of these valves the pressure under whichthe cracking operations are effected in one of the heating sections maybe different from that of the second section. It will further beunderstood that pumps, temperature intakes, controls and pressureregulators and other commonly used elements may be placed at appropriatepoints, as is well understood in the art.

By reason of the increased diameter and length of the second-stagecoils, I prefer that the reactions therein be under lower pressure thanin the first-stage cracking coils and vaporizing coils.

While I have described the preferred embodiment of my invention, it isunderstood that modifications will vary within comparatively Wide limitsprovided they do not depart from the scope and benefits of the inventionand claims. In fact, many variations may be made within the generalscope and extent of the invention as I have not I described my apparatusin a limiting sense.

The Venturi construction illustrated in Figure 2, in addition to itsapplication intermediate the vaporizing and second-stage cracking coils,may

be applied for controlling the flow of charging stock and steam to thevaporizing coil in either or both heating sections of the furnace. Thusthe injector tube may be carried by steam pipe 7 or steam pipe l2 andprojected within the appropriate charging stock pipe. By thisarrangement, pressure of the steam may be greater'than that of thecharging stock and hence may act as a conveyor for the charging stock,or vice versa.

What I claim is:

1. A dual two-stage cracking apparatus for hydrocarbon oils, whichcomprises a furnace divided by a wall into two heating sections, a wallin each section dividing the same into combustion and convection areaspermitting the passage of gases from the combustion area to theconvection area, a vaporizing coil at the lower portion of theconvection area of each heating section, means for leading a hydrocarbonoil charging stock to said vaporizing coil, a second-stage cracking coildisposed above each vaporizing coil, a first-stage cracking coil in eachcombustion area and comappropriate vaporizing coil, means whereby steammay be led from said superheater to the firstbustion section, and heatcontrol means for-the convection areas comprising'a plurality ofintercommunicating tubes disposed in said division wall between the twoheating sections, adapted to receive a relatively cool flow material andto lead the same to the vaporizing coils receiving hydrocarbon oilchargingstock. M

.. stage cracking coil, heating means in each com- 2. A crackingapparatus for hydrocarbon oils, which comprises a furnace, a wall in thefurnace dividing the same into combustion and convection areascommunicating at the top thereof, a vaporizing coil at the lower portionof the convection area, a second-stage cracking coil disposed above thevaporizing coil, a first-stage cracking coil in the combustion area andreceiving vapors from the vaporizing coil and discharging vaporsundergoing cracking reactions to the second-stage cracking coil, a steamsuperheater in the furnace and communicating with the vaporizing coil,means whereby steam may be led from said superheater to one of saidcracking coils, heating means in the combustion section, and a heatcontrol for the second-stage cracking coil comprising means forinjecting therein vapors directly from the vaporizing coil.

3. A cracking apparatus for hydrocarbon oils, which comprises a furnace,a wall in the furnace dividing the same into combustion and convectionareas communicating at the top thereof, a vaporizing coil at the lowerportion of the convection area, a second-stage cracking coil disposedabove the vaporizing coil, a first-stage cracking coil in the combustionarea and receiving vapors from the vaporizing coil and dischargingvapors undergoing cracking reactions to the second-stage cracking coil,a steam superheater in the furnace and communicating with the vaporizingcoil, means whereby steam may be led from said superheater to one ofsaid cracking coils, heating means in the combustion section, and heatcontrol means for the second-stage cracking coil comprising a Venturiinjector directly communicating with the vaporizing coil and projectingwithin said second-stage cracking coil.

4. A dual two-stage cracking apparatus for hydrocarbon oils, whichcomprises a furnace divided by a division wall into two heatingsections, another wall in each section dividing the same into combustionand convection areas permitting the passage of gases from the combustionarea to the convection area, a vaporizing coil at the lower portion ofthe convection area of each heating section, means for leading ahydrocarbon oil charging stock to said vaporizing coil, a secondstagecracking coil disposed above each vaporizing coil, a first-stagecracking coil in each combustion area and communicating with andreceiving vapors from the appropriate vaporizing coil, said first-stagecracking coil communicating with and discharging vapors undergoingcracking reactions to the second-stage cracking coil, the diameter andlength of the tubes comprising the first-stage cracking coil being lessthan that of the second-stage cracking coil whereby the vapors areexpanded in the second-stage cracking coil, a steam superheatercommunicating with the appropriate vaporizing coil, means whereby steammay be led from said superheater to the first-stage cracking coils,heating means in each combustion section, and heat control means for theconvection areas comprising a plurality of intercommunicating tubesdisposed in said division wall between the two heating sections, adaptedto receive a relatively cool fiow material and to lead the same to avaporizing coil of the two above specified, jointly with the oilcharging stock.

5. A dual two-stage cracking apparatus for hydrocarbon oils, whichcomprises a furnace divided by a division wall into two heatingsections, another wall in each section dividing the same into combustionand convection areas permitting the passage of gases from the combustionarea to the convection area, a vaporizing coil at the lower portion ofthe convection area of each heating section, means for leading ahydrocarbon oil charging stock to said vaporizing coil, a secondstagecracking coil disposed above each vaporizing coil, a first-stagecracking coil in each combustion area and communicating with andreceiving vapors from the appropriate vaporizing coil, said first-stagecracking coil communicating with and discharging vapors undergoingcracking reactions to the second-stage cracking coil, the diameter andlength of the tube comprising the first-stage cracking coil being lessthan that of the second-stage cracking coil whereby the vapors areexpanded in the second-stage cracking coil, a steam superheatercommunicating with the appropriate vaporizing coil, means whereby steammay be led from said superheater to the first-stage cracking coil,heating means in each combustion section, and a plurality ofintercommunicating tubes disposed in said division wall at the upperpart thereof opposite the second-stage cracking coils, and means forpassing hydrogenous gas through said intercommunicating tubes and to thevaporizing coils.

ERNEST A. OCON.

